Knees are subject to tremendous outside forces. As a joint centered in the leg, with long bones both above and below, the knee is readily damaged. A force against the side of the knee, which would cause no harm if applied to the hip or ankle, can readily tear internal knee ligaments. A rotational force carried through the ankle and hip without harm can cause internal knee rotation, snapping the ligaments that create knee stability.
The forces described above are an issue in sports, such as football, where external forces are frequently applied to the side of a player's leg. And where twisting is common due to stops, starts, and turns, with cleats preventing the foot from releasing and turning with the body.
What is needed is a device and method for protecting a knee from the external forces that cause internal damage.